Bottom Line:
No activity was found in kissing bug Rhodnius prolixus, mosquitoes Anopheles stephensi and Aedes aegypti, tse-tse fly Glossina fuscipes, stable fly Stomoxys calcitrans and human louse Pediculus humanus.Hyaluronidases of different insects vary substantially in their molecular weight, the structure of the molecule and the sensitivity to reducing conditions or sodium dodecyl sulphate.As this enzyme is present in all Phlebotomus and Lutzomyia species studied to date, it seems to be one of the factors responsible for enhancing activity present in sand fly saliva.

Background: Salivary hyaluronidases have been described in a few bloodsucking arthropods. However, very little is known about the presence of this enzyme in various bloodsucking insects and no data are available on its effect on transmitted microorganisms. Here, we studied hyaluronidase activity in thirteen bloodsucking insects belonging to four different orders. In addition, we assessed the effect of hyaluronidase coinoculation on the outcome of Leishmania major infection in BALB/c mice.

Conclusions: High hyaluronidase activities seem to be essential for insects with pool-feeding mode, where they facilitate the enlargement of the feeding lesion and serve as a spreading factor for other pharmacologically active compounds present in saliva. As this enzyme is present in all Phlebotomus and Lutzomyia species studied to date, it seems to be one of the factors responsible for enhancing activity present in sand fly saliva. We propose that salivary hyaluronidase may facilitate the spread of other vector-borne microorganisms, especially those transmitted by insects with high hyaluronidase activity, namely blackflies (Simuliidae), biting midges (Ceratopogonidae) and horse flies (Tabanidae).

pntd-0000294-g006: Effect of hyaluronidase on Leishmania infection in mice.BALB/c mice were coinoculated intradermally into ear with 104 or 105 Leishmania major and hyaluronidase equivalent to 0, 2 and 10 salivary glands of Phlebotomus papatasi. Lesion size, given as a product of its area (mm2) and the degree of ulceration (1–5), was monitored for 6 weeks post infection. Points (▪) = mean values, boxes = 95% confidence intervals, whiskers = min-max values. The p values of corresponding Kruskal-Wallis ANOVA are provided.

Mentions:
Next we examined whether hyaluronidase altered the course of Leishmania major infection in BALB/c mice. We used intradermal inoculation into the ear and the disease burden was calculated from weekly measuring the lesion size. As shown in Fig. 6, mice coinjected with parasites and hyaluronidase developed bigger lesions. In all groups of mice, the onset of lesion development was at three weeks p.i. Thereafter, the lesions grew faster in coinoculated groups. The experiment was terminated six weeks post infection when, in some animals, ulcerating lesion spread over the majority of ear pinna. In mice inoculated by higher parasite numbers (105), both hyaluronidase treatments produced similar effects (Fig. 6A). In mice with an inoculation dose one order of magnitude lower (104), the effect of hyaluronidase was concentration-dependent: lesions were bigger in mice coinoculated with hyaluronidase activity equivalent of 10 P. papatasi salivary glands than in those coinoculated with equivalent of 2 glands (Fig. 6B). In both parasite numbers (104 and 105) over all considered weeks (3 to 6) post-inoculation, Kruskal- Wallis ANOVA showed significant differences among hyaluronidase treatments (p always≤0.025), with only one exception in week 3 of 104 parasites treatment (p = 0.23). Consequently, the post-hoc comparison of treatments tests confirmed the significant difference between controls (no hyaluronidase) and corresponding inoculated hyaluronidase doses (2 or 10 glands equivalents). We also tested the difference between the 2 and 10 gland equivalent doses: however, despite the common trends apparent in Fig. 6 indicating that there may be a systematic difference between 2 and 10 gland equivalents doses, the post-hoc comparison of treatments test did not prove it in any case but in week 5 of the 104 parasites treatment.

pntd-0000294-g006: Effect of hyaluronidase on Leishmania infection in mice.BALB/c mice were coinoculated intradermally into ear with 104 or 105 Leishmania major and hyaluronidase equivalent to 0, 2 and 10 salivary glands of Phlebotomus papatasi. Lesion size, given as a product of its area (mm2) and the degree of ulceration (1–5), was monitored for 6 weeks post infection. Points (▪) = mean values, boxes = 95% confidence intervals, whiskers = min-max values. The p values of corresponding Kruskal-Wallis ANOVA are provided.

Mentions:
Next we examined whether hyaluronidase altered the course of Leishmania major infection in BALB/c mice. We used intradermal inoculation into the ear and the disease burden was calculated from weekly measuring the lesion size. As shown in Fig. 6, mice coinjected with parasites and hyaluronidase developed bigger lesions. In all groups of mice, the onset of lesion development was at three weeks p.i. Thereafter, the lesions grew faster in coinoculated groups. The experiment was terminated six weeks post infection when, in some animals, ulcerating lesion spread over the majority of ear pinna. In mice inoculated by higher parasite numbers (105), both hyaluronidase treatments produced similar effects (Fig. 6A). In mice with an inoculation dose one order of magnitude lower (104), the effect of hyaluronidase was concentration-dependent: lesions were bigger in mice coinoculated with hyaluronidase activity equivalent of 10 P. papatasi salivary glands than in those coinoculated with equivalent of 2 glands (Fig. 6B). In both parasite numbers (104 and 105) over all considered weeks (3 to 6) post-inoculation, Kruskal- Wallis ANOVA showed significant differences among hyaluronidase treatments (p always≤0.025), with only one exception in week 3 of 104 parasites treatment (p = 0.23). Consequently, the post-hoc comparison of treatments tests confirmed the significant difference between controls (no hyaluronidase) and corresponding inoculated hyaluronidase doses (2 or 10 glands equivalents). We also tested the difference between the 2 and 10 gland equivalent doses: however, despite the common trends apparent in Fig. 6 indicating that there may be a systematic difference between 2 and 10 gland equivalents doses, the post-hoc comparison of treatments test did not prove it in any case but in week 5 of the 104 parasites treatment.

Bottom Line:
No activity was found in kissing bug Rhodnius prolixus, mosquitoes Anopheles stephensi and Aedes aegypti, tse-tse fly Glossina fuscipes, stable fly Stomoxys calcitrans and human louse Pediculus humanus.Hyaluronidases of different insects vary substantially in their molecular weight, the structure of the molecule and the sensitivity to reducing conditions or sodium dodecyl sulphate.As this enzyme is present in all Phlebotomus and Lutzomyia species studied to date, it seems to be one of the factors responsible for enhancing activity present in sand fly saliva.

Background: Salivary hyaluronidases have been described in a few bloodsucking arthropods. However, very little is known about the presence of this enzyme in various bloodsucking insects and no data are available on its effect on transmitted microorganisms. Here, we studied hyaluronidase activity in thirteen bloodsucking insects belonging to four different orders. In addition, we assessed the effect of hyaluronidase coinoculation on the outcome of Leishmania major infection in BALB/c mice.

Conclusions: High hyaluronidase activities seem to be essential for insects with pool-feeding mode, where they facilitate the enlargement of the feeding lesion and serve as a spreading factor for other pharmacologically active compounds present in saliva. As this enzyme is present in all Phlebotomus and Lutzomyia species studied to date, it seems to be one of the factors responsible for enhancing activity present in sand fly saliva. We propose that salivary hyaluronidase may facilitate the spread of other vector-borne microorganisms, especially those transmitted by insects with high hyaluronidase activity, namely blackflies (Simuliidae), biting midges (Ceratopogonidae) and horse flies (Tabanidae).